White-light flares and why the chromosphere is different from the ionosphere

H. Hudson

Space Sciences Lab, UC

The chromosphere (the gap between the photosphere and the corona) is crucial in flare and CME development, and it should not be regarded as analogous to the ionosphere during auroral activity. The chromosphere is the lower boundary of the corona, but neither it nor the photosphere are good locations for a boundary surface for numerical calculations of coronal phenomena, since they evolve drastically during a flare. Much of the important physics remains to be explored. I discuss this in the context of recent observations of white-light flares and hard X-rays from TRACE and from RHESSI, respectively.